Calculate N using a high-precision method! And show n! (Factorial) value.

[Problem description]
For any given n value (N is an integer and 1 <= n <= 100), calculate and display n! (Factorial) value.
[Example]
Input: n = 10
Output: 3628800
Input: n = 20
Output: 2432902008176640000

Use an integer array to store every bit of a large number class and simulate the whole process of manual multiplication ..

# Include "stdio. H "# include" stdlib. H "const unsigned int max = 10000; // the maximum length of the integer array const long widthmax = 1000000000; // The maximum element width of the integer array Val [Max] is const unsigned int width = 9; // The format width of the output element of the integer array Val [Max, that is, the maximum number of digits of the elements of the integer array Val [Max] typedef struct node {long Val [Max]; // used to store the high-precision Integer unsigned int size; // actual length of the integer array} bigint; void printbigint (const bigint & A); // output bigint mulbigint (const bigint & A, const bigint & B); // multiply bigint facbigint (unsigned int N) by a big number class; // calculate the factorial void printbigint (const bigint & A) {unsigned W; int I; printf ("% LLD",. val [. size-1]); for (I =. size-2; I> = 0; I --) {W = widthmax/10; while (W> 0) {if (. val [I]> = W) break; printf ("0"); W/= 10;} printf ("% LLD",. val [I]);} printf ("\ n");}/* function name: mulbigint function: high-precision integer multiplication input parameter: const bigint &: high-precision Integer multiplier const bigint & B: output parameter of the high-precision Integer multiplier represented by an integer array: Bigi NT: return the high-precision Integer product */bigint mulbigint (const bigint & A, const bigint & B) {int I, j; bigint C; if (. size = 1 &. val [0] = 0) return a; If (B. size = 1 & B. val [0] = 0) return B; for (I = 0; I <Max; I ++) // All values are 0 C. val [I] = 0; for (I = 0, j = 0; I <B. size; I ++) {for (j = 0; j <. size; j ++) {C. val [I + J] + =. val [J] * B. val [I]; C. val [I + J + 1] + = C. val [I + J]/widthmax; C. val [I + J] % = widthmax;} C. size = I + J; If (C. VA L [C. Size]! = 0) // The highest bit has an inner C. size ++;} return C;}/* function name: facbigint function: high-precision Integer factorial input parameter: Unsigned int N: Positive Integer output parameter: bigint: returns the high-precision Integer factorial */bigint facbigint (unsigned int N) {unsigned long I; bigint S, C; C. size = S. size = 1; S. val [0] = 1; for (I = 2; I <= N; I ++) {C. val [0] = I; S = mulbigint (S, C);} return s;} int main (void) {bigint A; unsigned int N; printf ("Enter N value:"); scanf ("% u", & N); A = facbigint (n); printf ("% u's factorial is: \ n ", n); printbigint (a); System (" pause "); Return 0 ;}

Method 2:
 

# Include <iostream> using namespace STD; # define MAX 1000 int main (void) {int N; while (scanf ("% d", & N) = 1 & n> = 0) {int I, j; int A [Max]; // save count calculation result int P, add; // P stores the number of digits of the current result. Add is carry a [1] = 1; P = 1; for (I = 2; I <= N; ++ I) // loop with 2, 3, 4 ..... N multiplication {for (j = 1, add = 0; j <= P; ++ J) // multiply each of a [] by I {A [J] = A [J] * I + Add; add = A [J]/10; A [J] = A [J] % 10;} while (add> 0) // If H is not 0 {A [J] = add % 10; add = Add/10; + + J;} p = J-1; // assign the current number of digits to p} for (I = P; I> = 2; -- I) // the front of a [] array is a low position, followed by a high position {printf ("% d", a [I]);} printf ("% d \ n ", A [I]);} return 0 ;}